Does the Iliac Wing Influence L5 Pedicle Screw Fixation?

Abstract

To explore whether the iliac wing influences L5 pedicle screw (PS) fixation and to propose methods to reduce such influence. A total of 100 computed tomography scans (from 50 male and 50 female patients) of the lower lumbar region and pelvis were obtained and 3-dimensionally reconstructed. Cylinders with 6.5-mm diameters were drawn to simulate the different trajectories of L5 PS. The maximum lengths and lateral angles of trajectories, and the vertical distances from the inner edge of the iliac wing to these trajectories, were measured. The maximum lengths and lateral angles differed significantly among trajectories; the maximum length, but not the lateral angle, differed significantly between male and female subjects. The influence of the iliac wing was more significant in male than in female subjects. The iliac wing had a greater effect on screws implanted along the pedicle axis than on screws for which the trajectories commenced at Du's entry point and passed through the center of the pedicle. This study elucidates the influence of the iliac wing on L5 PS fixation. Careful attention is required when implanting PSs, especially in male patients. The combined use of Du's technique and a percutaneous method for PS implantation effectively reduces the influence of the iliac wing. To minimize the complications of PS fixation further, preoperative simulation of fixation for each patient is very important.